This invention relates in general to antifriction bearings and more particularly to an antifriction bearing that can withstand large parting forces in the axial direction.
With the advent of front wheel drive automobiles, automobile manufacturers have discovered that double row tapered roller bearings that are preset, sealed, and unitized are ideally suited for the front wheel assemblies of their automobiles. In this regard, front wheel drive automobiles are generally lighter than their rear wheel drive counterparts, but most of the weight is concentrated over the front wheels--indeed significantly more than in comparable rear wheel drive automobiles. This makes double row tapered roller bearings of compact envelope size ideally suited for front wheel drive automobiles, because such bearings are capable of carrying large radial loads as well as substantial thrust loads in both axial directions, all with a high degree of stability in a small space.
Automobile manufacturers find it convenient to have the bearings preset and unitized for handling purposes as well as prelubricated and sealed. This facilitates assembly of the front wheel units, for it avoids handling a multitude of bearing parts, and further eliminates all of the adjusting and lubricating problems.
In the typical front wheel drive assembly equipped with a tapered roller bearing, a double row bearing is used instead of two single row bearings as are often found in the front wheels of rear wheel drive automobiles. The double row bearing includes a double cup, that is a single cup or outer race having two raceways on it, which fits into a steering knuckle. The bearing also includes two cones which fit into the double cup from opposite ends and form an inner race. Of course there is a single row of tapered rollers between each cone and the cup, the rollers of each row being in the indirect orientation, that is with their large diameter ends presented outwardly away from the center of the bearing. The cones fit onto a drive flange, there being an interference fit between the cones and the drive flange to insure maximum stability. A powered drive axle extends through the drive flange, and a nut threads over the end of the axle to clamp the drive flange and the two cones on it together.
While double row bearings are, by reason of their unitized construction, easily installed in the front end units, they are difficult to remove without damaging them. The difficulty derives from the friction fit between the cones and the drive flange, for the outboard cone tends to remain with the drive flange as the drive flange is stripped from the bearing. Indeed, the outboard cone drives the rollers of the outboard row against the cage which in turn jams against the seal case or some structural member within the mounting, and the seal is usually damaged to the extent that the bearing is thereafter unable to operate satisfactorily. In the case of polymer cages, they will usually buckle under the thrust load that is transmitted through them and as a result may fracture. If this occurs, the rollers will damage the seal case and seal lips. Steel cages will on the other hand bend out of shape, permitting the rollers to contact and damage the seal.
Also, should the wheel nut be removed and the vehicle rolled about, as may occur during some servicing procedures, the cones of the bearing will tend to spread, due to the tapered geometry in the bearing, and may "walk off" of the drive flange. Thus it is desirable to construct the wheel unit and bearing so that this does not occur.